Beyond rugged: Plastic 'bleeds' when damaged, then heals itself

A team of scientists working on self-healing materials has produced a plastic that “bleeds” when scratched, stressed or torn and then heals itself, and can do so repeatedly.

The research, partly funded by the Defense Department, could lead to innovations such as smart-phone and tablet screens that fix themselves when cracked and aircraft parts that change color to warn of stress.

Marek Urban, a professor at the University of Southern Mississippi in Hattiesburg, presented his findings this week at the National Meeting & Exposition of the American Chemical Society in San Diego.

Urban’s team developed a thin, water-based copolymer that turns red when damaged and then can repair itself when exposed to light (from the sun or a bulb), pH changes or warm temperatures. He compared the process to what takes place with human skin or tree bark.

“Our new plastic tries to mimic nature, issuing a red signal when damaged and then renewing itself,” he said.

Chemists have made progress on self-healing materials in recent years with different approaches, Urban said during a streamed press conference.

What’s relatively new are materials than can repair themselves over and over — as opposed to just once — and what is unique about the plastics Urban’s team came up with is that it changes color when damaged, he said. And because it’s water-based, it’s more environmentally friendly that some other plastics.

Small molecular links “bridge” the long chains of chemicals within the plastic. When the material is scratched or cracked, the links break and, in this case, turn red. The red marks disappear when the plastic heals.

During the press conference, Urban, who said his work on the plastic started five to seven years ago, said the plastic is currently in the proof-of-concept stage but could be developed for a range of purposes, including pressure-sensitive devices that could change color when under pressure, self-healing nail polishes and screens for cell phones and laptops.

The plastic also could be made thicker and applied to any number of battlefield devices, including radios and weapons systems, as well as domestic infrastructure and vehicles. It could be applied to structural areas of aircraft, ships or bridges to warn of fatigue or damage. In some cases, engineers could decide whether to fix or replace a part simply by shining a light on it to see if it heals properly.

Back home, it could be handy to have self-healing car bumpers that might not survive a major accident but could withstand scratches and light dings.

Urban said that, in principle, that plastic should also heal when torn in half. “You can separate these materials out and they will self-heal,” he said during the press conference. The repairing process would only take minutes, and it can be repeated. “It can go many, many times,” he said.

The American Chemical Society’s announcement of Urban’s research points out that plastics have become pervasive in products and structures because of their light weight, strength and resistance to corrosion.

The downside has been repair in the case of damage. You can’t stitch, nail, bolt or weld plastic back together. And duct tape only does so much. But self-healing plastics could take rugged devices to an entirely new level.

About the Author

Kevin McCaney is editor of Defense Systems. Follow him on Twitter: @KevinMcCaney.